The present invention relates to a method and system for providing geographic specific services to a receiver in a satellite communications network. More particularly, the present invention relates to a method and system for providing geographic specific services to a receiver in a satellite digital audio radio service (SDARS) network by utilizing transmitter identification information included in a composite signal transmitted by a terrestrial repeater.
Satellite digital audio radio service (SDARS) is a satellite broadcast service recently approved by the U.S. Federal Communications Commission (FCC) which provides satellite transmission of digital audio programs to compatible radio receivers. The radio receivers can be stationary or mobile and are generally configured to receive composite broadcast signals comprising a plurality of data channels from satellites as well as terrestrial repeaters.
As shown in FIG. 1, SDARS provides service to a receiver or subscriber 4 over a nationwide coverage area through the use of two geostationary satellites 1 and 2 and a terrestrial repeater network comprising a plurality of individual terrestrial repeaters 3. In particular, SDARS employs a spatial and frequency diversity system wherein one of the geostationary satellites 1 transmits a first signal on one transmission channel and the other geostationary satellite 2 transmits a second signal containing the same program material as the first signal on a second transmission channel. Upon reception, the first and second signals are stored at the receiver 4 so that the two channels can be combined, or the program material in the two channels selected, via suitable receiver circuitry.
The terrestrial repeaters 3 receive the signals from the geostationary satellite 1 or 2, and retransmit the signals using multi-carrier modulation (MCM). The terrestrial repeaters 3 are used for coverage reinforcement in areas which receive poor satellite coverage. Signal reception can be disrupted at the receiver 4 due to physical obstructions which interfere with line of sight (LOS) reception between the geostationary satellites 1 and 2 and the receiver 4, or service outages. For example, mobile receivers may encounter physical obstructions when they pass through tunnels or travel near buildings or trees that impede LOS signal reception. Service outages can occur, on the other hand, when noise or cancellations of multipath signal reflections are sufficiently high with respect to the desired signal.
All of the terrestrial repeaters 3 of the terrestrial repeater network simultaneously transmit the same data to all subscribers (i.e., receiver 4) in the coverage area with the exception that each of the terrestrial repeaters transmits additional information which allows the receiver to identify the individual terrestrial repeater from which the currently received signal is originating. In particular, each terrestrial repeater adds to the retransmitted composite signal a unique transmitter identification number which is embedded after an MCM synchronization pattern. Presently, the transmitter identification number is generally used for RF network coverage analysis and field testing.
Although the nationwide coverage area comprises a plurality of distinct geographic areas (e.g., the northeast, the southwest, and so on), the ability to provide geographic specific service is not inherent with the above-described system architecture. That is, all receivers or subscribers receive the same broadcast data regardless of their geographic location. Accordingly, this inhibits the transmission/reception of geographically targeted data such a local weather forecasts, news, advertisements, and so on.
Accordingly, it is an object of the present invention to provide a method and system for providing geographic specific services to receivers in an SDARS network, wherein a receiver can provide different types of broadcast information to a user based on the geographic location of the receiver.
In accordance with the present invention, a method and apparatus are provided for transmitting and receiving geographic specific services in a satellite communications network by utilizing location identification information included in a composite signal transmitted by a terrestrial repeater. In particular, the terrestrial repeater receives from a satellite a composite signal comprising a plurality of time-division-multiplexed (TDM) data channels and retransmits the composite signal along with a unique transmitter identification number which indicates the identity of an individual repeater. Upon reception of the composite signal from the terrestrial repeater, a receiver determines the current geographical location of the receiver based on the transmitter identification number. The receiver then compares the current location of the receiver to header information of packets or frames carried within the data channels to select geographically targeted information in the data channels. The receiver then provides the selected information to a user of the receiver so that the user may receive services directed to audiences in the geographic location of the receiver.